not a vocaloid user (I use Myriad melody assistant virtual singer) but I imagine any voice to speech animation software could be used with vocaloid recordings as can any sound recordings.
Certainly iClone, Moviestorm and others even World of Warcraft, besides Daz and Poser have been used by singers for lipsync animation using their real voices.
Vocaloid produces a sound recording like any other.
They prob have an inhouse animation program for ease of use and extra income, using other content would depend on import/export options for that program.
I actually think something like Anime studio would be more their taste though.

I just downloaded the zips for the freeware program MikuMikudance to my Android, will install on PC later, busy rendering in Carrara at the moment.
I see it uses .x (directX files) earlier Carrara versions export to that, have C6pro installed, may see if I can at least open one of their models.
otherwise maybe Blender if one can actually use the blighter!
it is an animation program made for and used by Vocaloid users but not nessesarilly limited to that, likewise one could just as easily use Daz studio, Poser etc for Vocaloid voices.
I would not be using it for Vocaloid animation, has bullet physics I see and supports nVidia 3Dvision (the glasses to which I have yet to find a way to buy outside the United states!!!)

quick look
I can open the .x file props in Carrara 8pro
the figures use .pmd format (polygonmodelsomething generic to their program) so cannot open them except in MMD
simple one limb at a time posing and a timeline with render to avi seems to be the in program options
can only use vocaloid voice files for lipsyncn import/export options for content
might be plugins if one could read Japanese and explore thier site.

I realize my comments were off topic
but
since nobody has actually answered your question, a bump may to be to your advantage too!
Alexa, do you use MikuMikuDance at all?
I was wondering about the complicated copyright restrictions on the models that come with the program.
Japanese language is proving a barrier to fully understanding just what you are allowed to do.
I have since learnt on another forum how to get the figures rigged and animatable into both Carrara and iClone using a collada .dae plugin for PMDeditor
but if I cannot legally render them there, rather a pointless venture.http://www.youtube.com/watch?v=UCVnm1boITs
Miku Hatsume in iClone via fbx converter, Carrara 8.5beta and 3dx5.